Sealants useful in aerospace and other applications may be classified into pre-mixed frozen compositions (PMF) and two-part systems. In two-part systems, a first component contains a main polymer, such as a polysulfide polymer, together with a number of additional materials. The first component does not contain a curing agent, which is instead in the second component. The two components are manufactured, packaged separately, and mixed together immediately before use.
Unlike two-component systems which require mixing the curing paste and the base before use, PMFs may be cured by external factors, such as temperature. For this reason, PMFs must be frozen at, for example, −40° F. to −80° F. in order to suppress or slow down the curing reaction. When the PMFs are later brought to room temperature, the curing rate increases significantly. PMFs offer the convenience of being ready for use without mixing, and are therefore more cost- and time-effective than certain two-part systems. However, existing PMFs have limited shelf-lives and require storage at very low temperatures of −40° F. to −80° F. Indeed, existing PMFs require mixing of the base component and activator followed by immediate freezing to slow the curing reaction. Moreover, the PMF must be stored at the freezing temperature prior to use to slow curing. The need for freezing adds considerable manufacturing cost at least in additional labor and equipment. In addition, the composition must be transported and stored at the low freezing temperature (i.e., −40° F. to −80° F.), adding even more cost. Also, as freezing the composition merely slows the curing reaction, the PMF has a limited shelf life.